Worm-gearing



P. BROWN AND F. J. BOSTOCK.

WORM GEA RING APPLICATION FILED SEPT-18,1919.

1,349,81 1. Patented Aug. 17, 1920.

UNITED STATES PATENT OFFICE}.

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Specification of Letters fatent:

Application filed September 18. 1919. Serial No. 3 2l.549.

To allwhom it may concern Be it known that we, PERCY BROWN and FRANCISJOHN Bos'roox, subjects of King George V of Great Britain, residing atHuddersfield, in the county of York, England, have invented a new anduseful Improvement in Worm-Gearing, of which the following is aspecification.

This invention relating to worm gearing comprises an improvedconstruction or formation of the thread of they worm, or of the shapethereof, and has for its object the obtaining of an improvement of thecontact between the worm thread and the tooth of the worm wheel, one ofthe features of the improved construction or shape of thread being theelimination of a large portion of the usual slidin and rubbing contactfound in this type 0% same by a rolling action between the surfaces ofthe worm and Worm wheel while in engagement with each other.

It is usual in ordinary worm gears for the sides of the worm threadsupon a linear section, that is to say, a section obtained by a planecontainin the axis, to be made straight at a pre etermined angle. Suchformation, however, gives a worm whose motion is transmitted to the wormwheel by sliding action similar to that of movement along an inclinedplane or wedge. In order to obtain an increased load carrying capacity,there have been, of course, other forms or types of straight line wormthreads in which the straight line portion is on a plane not containingthe axis of the worm, but lying at a predetermined distance therefrom.

In the improved construction or shape of thread embodying our invention,we so form the sides of the thread that the motion from g the worm tothe wheel .is mainly that of a rolling action whereby we obtain a wormcapable of giving increased efficiency.

and will be particularly pointed out in the claims.

gear, and replacement of Figure 1 is an elevation, partly in sectiontaken ou a plane containingthe worm axis, of a worm constructedaccording to our invention, and

Fig. 2 is an enlarged transverse section of the worm thread.

Patented Aug. 17, 1920.

Referring to the drawingfiA, A represent the axis of the worm and B theroot or bottom diameter of the thread. Although not necessary for ourinvention B, B can suitably be made the axis of the hyperbole, thevertex of which is at the point a.

The formation of the hyperbola which constitutes eitherside of thethread is 'controlled or determined by its asymtote 0, b

the cutting of Worms, or it can be cut in the lathe by employing a toolwhose shape is identical to the required hyperbolic curve. and the wormwheel can also be out in the usual way by means of a hob made tocorrespond with the worm.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent is 1. A worm havin its thread so formed thatthe sides of sai thread, upon a section obtained by a plane containingthe axis, are portions of hyper-bolas, substantially as herein shown anddescribed and for the purpose set forth.

2. worm provided with a spiral thread the dleving face of side portionof which, upon a section obtained by a plane containing the axis'of theworm, is a portion of a hyperbole.

3. A worm having a thread with a workin surface shaped on its linearsection like a yperbola having an asymtote making an angle with the axisof the worm approxlmately equal to the angle of lead of the worm at theroot diameter.

4. A worm having a thread with a work ing surface shaped on its linearsection like proximately on the cylinder of the root 10 a hyperbolehaving an asymtote making an diameter of the three angle with the sunsof the worm having a In testimony whereof we afiix our signadefiniterelationship to the angle of lead tures in the presence of twowitnesses. of the worm at the root diameter. PERCY BROWN.

5. A worm the thread or teeth of which FRANCIS JOHN BOSTOCK. haveworking faces which form portions of Witnesses:

V hyperbolas in the plane of the axis of the CECIL SENIOR,

worm and having their vertices lying ap- LEONARD GIBSON SINBURN.

